The present disclosure relates generally to communications networks, and more particularly, to building a backup tunnel for forwarding data following a failure in the communications network.
Following a network failure (e.g., link or node failure), a node adjacent to the failure will attempt to find an alternate path to a destination. However, this requires time and may cause the node to drop packets being routed to the destination while the network converges. There are many applications which require a non-looping mechanism to route around a network failure and drop a minimal number of packets while the network is converging. Fast reroute techniques have been developed to assure rapid recovery in the event of a network failure. Fast reroute requires a node to compute a backup tunnel (path) around a possible failure. When a failure is detected, the node forwards subsequent packets which otherwise would have traversed the failure, via the backup tunnel. Traffic flowing through a failed link or node is thus rerouted through one or more preconfigured backup tunnels through the use of fast reroute. Redirection of the impacted traffic occurs very quickly to minimize impact on the user experience.
As described above, fast reroute requires identification of a backup path, however, there is not always an indication of which neighbor nodes should not be used in the backup path. In some fast reroute processes, a node must wait to receive advertisements and create a map of the network topology before constructing a backup tunnel.
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